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    Subject[PATCH 08/16] writeback: inline allocation failure handling in bdi_alloc_queue_work()
    Date
    This gets rid of work == NULL in bdi_queue_work() and puts the
    OOM handling where it belongs.

    Acked-by: Jan Kara <jack@suse.cz>
    Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
    ---
    fs/fs-writeback.c | 49 +++++++++++++++++++++++++++----------------------
    1 files changed, 27 insertions(+), 22 deletions(-)

    diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
    index f8cd7a9..59b3ee6 100644
    --- a/fs/fs-writeback.c
    +++ b/fs/fs-writeback.c
    @@ -149,21 +149,19 @@ static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work)

    static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
    {
    - if (work) {
    - work->seen = bdi->wb_mask;
    - BUG_ON(!work->seen);
    - atomic_set(&work->pending, bdi->wb_cnt);
    - BUG_ON(!bdi->wb_cnt);
    + work->seen = bdi->wb_mask;
    + BUG_ON(!work->seen);
    + atomic_set(&work->pending, bdi->wb_cnt);
    + BUG_ON(!bdi->wb_cnt);

    - /*
    - * Make sure stores are seen before it appears on the list
    - */
    - smp_mb();
    + /*
    + * Make sure stores are seen before it appears on the list
    + */
    + smp_mb();

    - spin_lock(&bdi->wb_lock);
    - list_add_tail_rcu(&work->list, &bdi->work_list);
    - spin_unlock(&bdi->wb_lock);
    - }
    + spin_lock(&bdi->wb_lock);
    + list_add_tail_rcu(&work->list, &bdi->work_list);
    + spin_unlock(&bdi->wb_lock);

    /*
    * If the default thread isn't there, make sure we add it. When
    @@ -175,14 +173,12 @@ static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
    struct bdi_writeback *wb = &bdi->wb;

    /*
    - * If we failed allocating the bdi work item, wake up the wb
    - * thread always. As a safety precaution, it'll flush out
    - * everything
    + * End work now if this wb has no dirty IO pending. Otherwise
    + * wakeup the handling thread
    */
    - if (!wb_has_dirty_io(wb)) {
    - if (work)
    - wb_clear_pending(wb, work);
    - } else if (wb->task)
    + if (!wb_has_dirty_io(wb))
    + wb_clear_pending(wb, work);
    + else if (wb->task)
    wake_up_process(wb->task);
    }
    }
    @@ -202,11 +198,20 @@ static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
    {
    struct bdi_work *work;

    + /*
    + * This is WB_SYNC_NONE writeback, so if allocation fails just
    + * wakeup the thread for old dirty data writeback
    + */
    work = kmalloc(sizeof(*work), GFP_ATOMIC);
    - if (work)
    + if (work) {
    bdi_work_init(work, wbc);
    + bdi_queue_work(bdi, work);
    + } else {
    + struct bdi_writeback *wb = &bdi->wb;

    - bdi_queue_work(bdi, work);
    + if (wb->task)
    + wake_up_process(wb->task);
    + }
    }

    void bdi_start_writeback(struct writeback_control *wbc)
    --
    1.6.4.1.207.g68ea


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